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Abstract
This review paper deals with the current statues of pre-treatment quality assurance conducted for Intensity modulated radiation therapy. Focusing on the issues relevant to two-dimensional verification of absorbed dose distribution, review was made for the papers published during the last 3∼4 years. Lastly, the future development direction was projected.
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Fig. 1.
Example of the gamma index and parameter selection of the gamma index, (a) histogram of the gamma map wit 5%/3 mm criteria (b) DTA/DD criteria satisfying P (DTA, DD) 90%.20)
Fig. 2.
Dose shifting and c index passing rate. (a) A 2-cm strip curve shifted 1 mm and (b) a 2-cm strip shifted 2 mm.20)
Table 1.
Average passing rate and standard deviation of the IMRT QA results for 53 fields for the three photon beam models. The measurement was performed with the MapCHECK device. IMRT plan was generated using the BM4 beam model for each patient. The same beam parameters MUs, segment weights, etc were then employed to distributions with each of the three beam models. %Diff and DTA acceptance criteria were used to evaluate the agreement between calculated and measured dose distribution. 12)
| CC13 model (BM6) | CC04 model (BM4) | Deconvolved∗ model (BM08) | |
|---|---|---|---|
| 2%/2 mm | 81.6±7.8 | 92.6±3.3 | 96.8±2.3 |
| 3%/3 mm | 93.8±4.1 | 98.9±1.0 | 99.4±0.6 |
Table 2.
Pearson correlation values r and two-tailed p-values correlating the magnitude of anatomy dose errors to three IMRT QA Gamma passing rate performance metrics. Significant p-values ＜0.01 are italicized for emphasis. Note: The statistically significant correlations have positive r-value positive slope indicating that the highest critical dose errors happen at the higher Gamma passing rates.18)
Table 3.
Pearson product-moment correlation coefficient (r) and two-tailed p-values correlating the magnitude of anatomy dose errors to gamma passing rates over three sets of gamma criteria. In all cases, the percent difference normalization was local to maximize sensitivity, and the lower threshold for analysis was 10% of the global maximum dose. PDP correlation coefficients are also shown for comparison.21)
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